Clandestine nuclear weapons are an immediate worldwide threat. Rogue nations with nuclear weapons, or terrorist groups acquiring radiological material, could deliver it to a victim nation via commercial shipping. Advanced radiation detectors are necessary to reveal such weapons among shielding and clutter. An urgent national priority is the development of radiation detectors that detect shielded radioactive threats. In addition to detecting the presence of a threat source, it would be highly advantageous to also determine the location of the source. The location information would greatly improve the reliability of the detection, while greatly reducing false alarms. To be most effective, the detector should locate the source in two dimensions, such as horizontal and vertical angles or azimuthal and polar angles, relative to the detector.
An advanced gamma ray or neutron detector with two-dimensional directionality would be a huge advantage for safety and security applications, because it would greatly speed up the inspection process, would reveal hidden sources with higher sensitivity, and would enable rapid clearing of clean loads automatically. Even a shielded source would be revealed by particles coming from a particular spot on the cargo, as opposed to a broad background distribution. In this way, the two-dimensional localization greatly accelerates the scan and greatly amplifies the reliability of the alarm. In addition, the revealed location would provide a valuable starting point for the secondary inspection team. With such a detector, the entire inspection process could be speeded up, resulting in greatly reduced inspection times and reduced entry waits at shipping ports. And more importantly, it would detect a smuggled weapon.
What is needed, then, is an integrated radiation detector system with two-dimensional directionality. The detector should indicate, on a single measurement, the full two-dimensional source direction without rotations or iteration. Preferably such a detector would be compact, light-weight, fast, highly efficient, capable of high angular precision, and preferably with low cost.